1. Field of the Invention
The invention provides an improved connection for sealably joining two members. More particularly, the invention relates to a leakproof union coupling, which may be used, for example, in a refrigeration system.
2. Description of the Prior Art
Refrigeration systems typically include several components, such as compressors, condensers, heat exchangers, and valves, which must be connected together in a way that effectively seals the interior of the refrigerant circulating system from the environment around it. Refrigerants, such as Freon, which are introduced into such systems as the working fluid, are expensive, hazardous to the environment, and sometimes toxic, and it is therefore critical that a closed circulating system be effectively sealed to prevent escape of the fluid or gas.
Sealing of a refrigeration system is often complicated by the fact that various portions of the system are simultaneously hot and cold, and may be operated under a high pressure and a vacuum, and vibration is often a factor. Also, the common refrigerant fluids may be incompatible with many common sealing materials, and specialized materials such as polytetrafluoroethylene (TEFLON) must be used.
It is often desirable that a connection between two components of a refrigeration system be easily disconnected, so that installation and replacement of a component may be accomplished without the use of heat connecting methods or extensive tools. It is also desirable that the connection be accomplished by abutting the ends of two fixed conduits and sealably joining them, without rotating either conduit. Connections known as xe2x80x9cunionsxe2x80x9d are common in plumbing and other pipefitting arts, which employ a rotatable nut or collar to connect abutting ends of conduits, where the ends have been previously fitted with appropriate hardware. The typical union may be repeatedly connected and disconnected by rotating the collar.
As described in U.S. Pat. No. 5,131,695, commonly assigned with the present application, the disclosure of which is hereby incorporated by reference, one manner of joining conduits is by providing a variable width seal within the union. Such seal includes a washer disposed between two metal portions of the union so that the two metal portions do not contact each other in normal usage. That is, the compressed washer is the primary sealing mechanism, and such seal may be backed up by metal on metal contact only on failure of the compressed washer. While this arrangement is generally suitable, several potential problems exist.
First, the compressed washer is manufactured preferably from TEFLON, and more preferably glass filled TEFLON. The washer tends to suffer from relaxation of tension with time due to cold flow of the seal material. Second, the secondary metal on metal seat is purely compressive in nature, and allows for some small degree of leakage if one or both of the metal parts are damaged during handling. Further, if the compression is insufficient to fill any gaps in the metal, a small but detectable leak can result. If such a leak were to develop, the union may require disassembly and possible replacement, a process that may involve loss of refrigerant and increased costs. Thus a need exists for a more robust sealing mechanism for a union or coupling.
In one embodiment, the present invention is an apparatus having a body with first and second ends, one of which has an annular protrusion extending therefrom. The apparatus further has an adapter with an axial groove dimensioned so that an outward edge of the groove contacts the annular protrusion of the body while the body is coupled to the adapter. A seal ring is disposed within the axial groove. In operation, the apparatus may be coupled, such as by a tensioner, so that a metal to metal seal is made between the body and the adapter that acts as a primary seal, while the seal ring, portions of which may be extruded out of the axial groove, acts as a secondary seal.